Centrifugal compressor stability means



Patented May 24, 1949 2,411,174 cEN'rmFUGAL COMPRESSOR s'miu'rr MEAN William E. Trumpler, Olean, N. Y., assignor to Clark Bros. Co., Inc., Olean, N. Y., a corporation of New York Application April 24, 1947, Serial No. 743,549

This invention relates to centrifugal compresimpeller, of a tendency to discharge at higherl velocity at one end than at the other, attained as by constructing the impeller of greater diameter at the higher velocity end; and location of the recirculation flow path adjacent the other end of the impeller, at its periphery-so that, generally, the recirculation lflow path is displaced from the principal path of discharge from the impeller into the diffuser.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, wherein Fig. l is a typical sectional view of pertinent parts of a compressor embodying the invention, the axis of the compressor being disposed in the plane of the section, and

Fig. 2 is an endwise fragmentary view of the impeller of Fig. 1.

With reference now to the drawings, A is the shaft of the compressor on which is mounted, to be driven thereby, an impeller generally indicated at B. C represents generally diffuser means into which the impeller B discharges; it being understood, as well known in the art, that the diffuser C is stationary and associated with bearings for the shaft A, and further that the parts illustrated may represent but one of several stages of the compressor.

More particularly as to the impeller'B, it comprises a pair of end members I and 2 between which extend a number of blades 3 and to both of which the blades are secured. The manner of such blade securement is not materia1 to this invention, but as here shown it includes flanges on the blades bearing against and connected to the end member faces as by rivets indicated Fig. 2.

The end member I includes a hub portion extending to the shaft A and there having driven connection by means not appearing in the draw 6 Claims. (Cl. 230-127) ing; and the end member 2 is in the form of an annular disc, to provide a central inlet opening.

The blades 3 support the disc end member 2 on the hub end member I, and are disposed to have their principal extent radially and longitudinally of the shaft A, but with rearward slope with reference to the direction of rotation as indicated by the arrow, Fig. 2.

The diffuser C comprises a pair of walls 5 and 6 spaced to provide a diffuser passage 1 annular about the impeller to receive the discharge therefrom.

:What has thus far been described is generally old and well known in the art. Inv its operation, when the impeller B is driven, centrifugal force will cause flow axially as indicated by the arrow A, thence radially as indicated by the arrow B to the 'impeller periphery. Therefrorn flow is divergently through the passage 1 of the diffuser, as indicated by the arrow C, the diffuser serving to convert kinetic energy imparted by the impeller, into pressure energy at the extremity of the passage 1.

According to this invention, means are provided for stabilizing compressor operation under conditions of low demand.

To this end, as here shown as to the impeller B, the outer diameter of the hub end member lof the impeller is somewhat greater than that of the disc end member 2; and at their outer extremities the blades 3 are so contoured, as at 3a, that each blade is radially coextensive with each end member where the blade joins the latter.

Preferably, the outer extremity of the blade is, for the major portion of its axial length, coextensive with the hub end member I, the blade extremity joining the disc end member 2 with slope as indicated in the drawings. Preferably also, the blades may be slightly canted as indicated Fig. 2, so that their effective edges along the disc end member 2 have slight lead over those along the hub end member I.

The result of such impeller construction is that the impeller will have a tendency to discharge at higher velocity adjacent its hub end member I than adjacent its disc end member 2; -such tendency effectively increasing as demand upon the compressor decreases, and substantially disappearing as the maximum impeller output is attained.

As to the diffuser C, according to this invention, its wall 5, corresponding to the disc end member 2 of the impeller B, is ,deformed to provide an cess commences immediately adjacent the periphery of the disc end member 2, becomes maximum slightly downstream thereof approximately opposite the periphery of the hub end member I', and thence gradually merges into the straight principal wall part bounding the passage 1.

The result of the arrangement described is that, at light loads on the compressor, a recirculation iiow path is provided as indicated by the small arrows Fig. 1, leading, generally, radially from the impeller, thence toward the diffuser wall 5, thence radially inwardly within the recess 5a, and thence returning to the impeller radially short of its radial extremity; such recirculation path being displaced, endwise of the impeller, and to the left Fig. 1, from the principal straight iiow path from the impeller to the diffuser.

The amount of flow in the recirculation path will automatically vary with the demand upon the impeller, recirculation increasing at light impeller loads, and being negligible at full compressor load.

It may be observed that, in eifect, the invention provides, for recirculation, a secondary endwise inlet to the impeller located thereabout and slightly within the radial impeller extremity which is at the opposite end of the impeller, the diffuser recess directing recirculation flow to the impeller at such secondary inlet.

What I claim is:

1. A centrifugal compressor including cooperative impeller and diffuser means, said impeller having a. pair of circular end members with blades disposed therebetween, and said diiuser -means having a pair of walls disposed to receive therebetween discharge from said impeller, one of said impeller end members being of less diameter than the other, and the corresponding diiuser wall being annularly recessed thereadj acent, to provide a flow path for recirculation at low capacity operation of said compressor.

2. A centrifugal compressor including cooperative impeller and diiuser means, said impeller having blades and said diifuser means having a pair of walls disposed to receive therebetween discharge from said impeller, said blades, endwise of the compressor being of less radial extent adjacent one of said diffuser walls than the other, and said diffuser wall being recessed adjacent the impeller periphery to provide a recirculation ow path.

3. A centrifugal compressor includingv cooperative impeller and diifuser means, said impeller having a pair of circular end members with blades disposed therebetween, and said diffuser means having a pair of walls disposed to receive therebetween discharge from said impeller, one of said CTI end members and the-adjacent portions of said blades extending radially short of the other end member and its adjacent blade portions, and the diiuser wall adjacent said shorter end member being recessed opposite the periphery of said impeller, to provide a recirculation W path.

4. A centrifugal compressor including cooperative impeller and diffuser means, said impeller having a pair of circular end members, one of said end members having a hub portion and the other being of lesser outside diameter and having a central inlet opening, and said impeller including blades extending between said end members, said diffuser means having a pair of walls disposed to receive therebetween discharge from said impeller, the diffuser wall nearer said smaller end member being recessed adjacent the periphery thereof, toprovide a recirculation flow path.

5. In a centrifugal compressor having cooperative impeller and di'user means, said impeller having blades providing peripheral discharge and said diifuser having a passage arranged to receive said discharge, said impeller having less radial extent at one end than at the other, the wall of said diffuser nearer the lesser end of the impeller being recessed adjacent the impeller periphery,

, to provide a recirculation flow path.

6. A centrifugal compressor including cooperative impeller and diffuser means, said vimpeller having end members and blades therebetween and being of less radial extent at one end than at the other to provide a secondary recirculation inlet endwise of the impeller peripherally about and immediately radially beyond the lesser impeller end, and said diffuser having a recess adjacent the periphery of said lesser impeller end arranged to diret recirculation flow toward said secondary inle WILLIAM E. TRUMPLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATESl PATENTS Number Name Date 1,161,926 Criqui Nov. 30, 1915 2,096,883 I Clason Oct. 26, 1937 2,245,179 Boivie June 10, 1941 2,362,514 Warner Nov. 14, 1944 2,399,072 Thompson Apr. 23, 1946 FOREIGN PATENTS Number Country Date 318,263 Great Britain Feb. 27, 1930 

